Re: Major overhaul of the RDFa primer

Hi Ivan,

Great work. Minor comments below.



On Fri, Sep 9, 2011 at 11:03 AM, Ivan Herman <ivan@w3.org> wrote:

> Guys,
>
> based on the comments of the other day, I have made a pretty major overhaul
> of the RDFa 1.1 primer, see
>
> http://www.w3.org/2010/02/rdfa/sources/rdfa-primer/
>
> The goal, if you remember, was to put the vocab feature to the fore, and
> push the prefix possibilities a little bit into the background. That is
> essentially what I did; however, this created a cascade of changes, it was
> not only a simple reshuffling of the paragraphs. Indeed, the previous
> version of the Primer was based on the Open Graph Protocol of Facebook. Of
> course, it would have been possible to turn that around with vocab but, as
> we know, Facebook only recognizes the prefixed version, ie, og:title and
> friends. I think it would be really bad to use this example with vocab,
> knowing that nobody would ever use that in practice because that is not what
> Facebook recognizes. This meant that I had to redo all the examples, and I
> used, primarily, the Dublin Core properties as a primary vocabulary. I also
> added a separate section on multiple vocabularies, where I introduce
> prefixes; to make that part of the message even stronger, I also added some
> SIOC terms to the example (ie, to have an example using many different
> vocabularies).
>

That's good, I think it illustrates well when prefixes are required (and
when vocab alone is enough). Note that the first OGP example with full URIs
is not something that will be parsed ok by Facebook afaik. Maybe you could
swap og and dc in this particular example, so full URIs are never used for
OGP (use full URIs for dc instead)?


>
> As an independent issue, I have also added a separate section on the usage
> of @resource. The recent discussion around @itemref, and the examples given
> by Stéphane and Lin Clark on how @itemref is used in the Drupal+microdata
> version and, more importantly, how the very same example can be encoded in
> RDFa using @resource and @about shows that the @resource-@about pattern is
> very important in practice. Ie, having a separate section on that is really
> good, so I added one.
>
> As I said, this meant a major reshuffle of sections, change of examples,
> diagrams, etc. In other words, all kinds of error prone operations. I would
> really appreciate if some of you guys read the text and listed the bugs,
> misspellings, etc, that are undoubtedly there...
>
> *If* we have lists in RDFa, I think a separate section on them (in the
> advanced features) would be worth adding. There is nothing at the moment on
> datatypes; I am not sure it is really necessary but maybe it is... Other
> than that, I feel that the primer is in a pretty good shape (modulo the
> problems you guys may still find).
>


s/licencing/licensing

[[[
A Blank Node: blank nodes are not identified by URL. Instead, many of them
have an RDFa typeof attribute that identifies the type of data they
represent. This approach—providing no name but adding a type—is particularly
useful when listing a number of items on a page that have no permanent URL,
e.g., calendar events, authors on an article, friends on a social networfk,
etc.
]]]

s/networfk/network

I read this as an encouragement to using blank nodes. I think we should
encourage the use of identifiers and only encourage blank nodes when
appropriate. Earlier in the document, some advantages are given for using
URIs as opposed to ambiguous tokens like 'title' or 'created'. I think the
primer should follow this for data items too. Social networks is a good
example where using or reusing URIs for people is good and prevents
ambiguity (many social networds provide URIs for profiles, even if not all
of them are typed foaf:Person). Or did you purposely leave out the @about to
avoid opening the foaf:Person/foaf:Document can of worm, in other words to
avoid people from asserting that homepages are foaf:Person's?

[[[
Figure 9: Structrure of Alice’s Site:
]]]
s/Structrure/Structure

Steph.